Successful definition of nanowire and porous Si regions of different porosity levels by regular positive photoresist using metal-assisted chemical etching

A simple and efficient method for selective formation of porous Si areas using regular photoresist as a masking layer is presented. Such a simple masking layer is sufficient to create a wide range of porosity levels through metal-assisted chemical etching (MaCE) using platinum, palladium and silver nanoparticles. Reproducible porous areas with a minimum feature size of 5 ?m were produced on Si wafers. The pore size and height are the functions of the etching time and type of nanoparticles. Using Ag nanopaticles we have been able to obtain Si nanowires of about 30 ?m height. Based on these results, a combination of positive photoresist and MaCE seems to be a reliable way for micron and submicron patterning of nanowire and porous areas on Si wafers, which is simple, inexpensive and compatible with integrated circuit fabrication techniques.